The Siemens 5SL7240-8RC is a miniature circuit breaker (MCB) rated at 415 V, 2-pole, with a 10 kA breaking capacity and a D-curve trip characteristic at 40 A.
Snap-on DIN rail mount for standard 35 mm rail. Two-pole form factor occupies two module widths (roughly 36 mm). Rated for 415 V line-to-line, so it covers three-phase branch circuits where each pole protects a phase conductor.
The D 40 marking on the front face tells the installer the trip curve and amp rating at a glance — no need to cross-reference the order code during commissioning or fault isolation. For a 40 A D-curve MCB, expect the magnetic trip to operate between 400 A and 800 A, clearing fast on hard short circuits while passing motor-start transients.